Dynamoelectric machine cooling



March 15, w J, ELK 2,464,221

DYNAMOELECTRIG MACHINE COOLING Filed Sept. 27, 1945 Patented Mar. 15, 1949 UNITED STATES PATENT OFFICE amended April 30, 1928; 370 O. G. 757) This invention is an improvement for increasing the life and improving the operation of aircraft engine accessory bearings such as the inner generator shaft bearings used in the aircraft accessory mount described in my copending application Serial No. 572,504, filed January 12, 1945, now Patent No. 2,450,422, patented October 5, 1948.

In that application an invention is defined wherein means are provided to facilitate the alignment of the drive shaft of a generator or starter of an engine with the power take-off shaft of the engine to which it is attached, in such manner as to permit rapid dismantling and reassembly of the generator or starter without the use of shims or adjustable elements. It shows a combination similar to the one used in the present device, comprising a driving element and a driven element removably attached thereto and means associated with one of said elements cooperable with the other element to insure alignment of the other element with said one element upon assembly, the alignment being insured merely by the assembly of the other element in cooperation with said means. More specifically, a sleeve is fixed with respect to the driving element and has internal bearing surfaces concentric with respect to the axis of the driving element, and the unit to be driven has bearing surfaces cooperating with the bearing surfaces in the sleeve, the bearing surfaces of the unit being concentric with the driving shaft so that when the unit is mounted in the sleeve the driven element and the driving shaft will be in perfect alignment. An annular space is left between the unit and the sleeve through which air may be forced to provide cooling, openings being formed in the sleeve adjacent to its closed end thereby to permit the cooling air to be discharged.

Tests of this construction have indicated that the inner shaft bearings of the generator have failed in some instances due to high bearing temperatures caused by high speed, high generator electrical load, or a combinat on of both. There were also indications that the internal cooling air pressure tended to force the grease out of the bearings while this grease was in a liquid or semi-liquid state as a result of the high temperature conditions described above. Consequently the bearing lubrication became insufilcient, causing excessive heating and eventual failure.

The object of the present invention is to rectify the conditions causing failure of the bearings, by cooling of the bearing and equalization of the air pressures on both sides of the bearing.

A further object is to provide means for cooling and improving the lubrication of internally mounted bearings particularly for accessory drive shafts such as engine operated generators, engine starters, etc.

A further object is to provide air passages at the internal end of a generator mount, wherein the generator is provided with an air impeller at its inner end, the passages providing for conducting some of the air from said impeller through a large port in the wall separating the two sides of said bearing, then through a restricted opening outwardly to the atmosphere, whereby the bearing is not only cooled. by said air flow, but the pressure on both sides of said bearing is equalized, so as to prevent expulsion of the grease therefrom such as referred to above.

Other and more specific objects will be apparent from the following detailed description of the present invention, which is illustrated in the accompanying drawings.

Fig. 1 is a partial view of a generator mounted in place and having means for aligning its shaft with the driving means such as is defined in my copending application, but provided with an illustrative form of the present improvement.

Figs. 2, 3 and 4 are partial sectional views taken at the correspondingly numeraled section lines of Fig. 1.

The generator mount l l is attached to the engine by mounting studs and nuts M, a spacer Ill being interposed under said mount against the engine cas ng. Mounting lugs l2 have internal bearing surfaces concentric with the drive shaft are mounted at spaced intervals around the outer edge of said mount by means of mounting bolts it. The inner surfaces of these mounting lugs are made to fit the outer surface of the generator casing 56. The casing I5 has a base or end plate, which is fitted into the bottom of the mount and supports the inner end bearing of the generator shaft. A fan is mounted on the generator shaft and has radial impeller blades, the outer ends of wh ch have a small clearance between them and the inside of the generator casing, so as to provide a passage for some of the air forced outwardly by said blades to enter the space between the impeller blade end plate and the inner bearing support wall of the base of the generator casing. Openings 253 are formed in this wall for admitting this air into the space on the other side of said bearing, and more restricted openings 2! are provided in the cylindrical flange l5 of the generator base to permit the air to flow out into the inside of the generator mount and then into atmosphere. An annuiar clearance space is provided between the outside of the generator casing and the inside or the generator mount for the passage of cooling air from the outer end of said mount through the space between the mounting lugs i2 and out through the tangential ports I 8, which register with similar ports in the generato-r casing opposite the generator fan. Air is drawn in through the air blast intake i? and follows the path indicated by the arrows in Fig. 1, through the generator between the armature and field assemblies, into the fan impeller hlading where it is forced radially outwardly through the ports it? while some of it is diverted into the chamber through the clearance space previously referred to, and goes through the ports 253 and 1' into the space it, whereirom it is drawn by suction into the outgoing air-stream through the ports it. Ports iii are provided at the base of the generate-r mount for admitting additional cooling air into the reduced pressure chamber 25 where it joins the stream of air coming in through the ports 2i and flows out into the ports I8. The cylindrical flange E5 on the base of the generator casing helps to align the generator in cooperation with the aligning surfaces provided by the mounting lugs ill. The generator is held in place when mounted by lug attaching bolts The ports it are staggered circumferentially in relation to the ports ii. The studs shown may be the existing engine parts, to which the mount is adapted. The nuts I are so related to the flange is that they are self locking when the flange is in place, thus eliminating the necessity of safety wiring of said nuts.

Because of the use of the ports 2! and the restricted ports 2! the air pressure in the area is substantially the same as in the area 26%. The above design maintains pressure in the area 225 which tends to oppose oil leakage from both the driving and the driven units; and if leakage of oil into the area 25 does occur, the air pressures are such as to force the oil out of this area into the area 25, out of the assembly through the air outlets 553. By holding the Fig. 1 upside down, it will be seen that the above described. elimination of oil will occur by gravity, if e supply of cooling air is interrupted.

It will be seen that by making the alignment flange E5 of suitable light weight metal, this reduction in weight combined with the increase of capacity of the generator, when used with. this accessory mount, may result in a lower overall Weight kilowatt than formerly obtained with standard mounts.

Although the improvement is shown in connection with the generator mount for internal fan type generators, it is obvious that this construction is applicable to mounts and bearings for other accessories involving similar problems. It is also obvious that many modifications in form and arrangement of parts may be made in the construction shown without departing from the spirit and scope of the present invention, as defined in the appended claims.

The invention described herein may be manufactored used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor. 5 What is claimed is:

1. In a generator mount for an internal fan type generator having means for aligning said generator vith the drive including a cylindrical extending from the base of the generator, p )herally spaced tangential ports n said generator casing and mount ali ed with said is." there being some clearance between said fan a d generator casing for lay-passing some of the cooling from the periphery of said fan to the back of the nnular wall in the base i g nerator supporting the inner generator shaft bearing bacl; of said fan, enlarged ports in said wall and restri ted ports in said flange leading to the atmosphere.

2. In a gei'- ator mount for an internal fan type gener-ato generator cylindrical fia V .al ports in mount a gned with said fan generator for e of the cooling air from the peripfan to the ba oi the Ian, an annular wall in the base of generator Ell ng the generator shalt be g l: of said fan, enlarged ports in said well restrict ports in said ii ge lead ing to the atmosphere, an anr clearance space around generator cas r mount "for lead v adcli .Li coo on the outer end of said mount into said tangen :5. A cornlziinat on such as clei'll whercin ann chamber is i the gener or casing said res ports and perip y back of .g flange. leading into said chamber, ports in the base of the id ch l'li" rzh by air into from said restric ed ports and and the periphery of the mount is ii! at ports otecl through tr e clearance around the erator into sed tangential ports.

. accessory by an annular fl .nge ext .nding inwardly g the inner end oi saio accosi or admitting s."- aid out flange to the other side s flange then passing it nto the atmosphere. WILLIAM J. ELKS.

-Allen June 3, 1919 Bogaty -l Apr. 9, 1940 Number 

